The allocation of calls given by elevator users to the different elevators of the elevator system is one of the basic tasks of the control of the system. The purpose of allocation is to give calls for the elevator cars to serve such that one of the desired performance indicators describing the operating ability of the elevator system is as good as possible. Conventionally the most commonly used performance indicators are e.g. passenger waiting times and travel times. Typically averages are calculated from these times and their distributions are established. In this context the term ‘calls’ is used to refer generally to all calls given—i.e. both the calls given with the up-down buttons situated on landings and the destination floor calls given in the elevator cars. The former are landing calls and the latter are car calls. In addition, calls can be calls given by call-issuing devices according to the so-called destination control method. In the destination control method the elevator user gives his destination floor to the system data with the call device already in the elevator lobby and in this case there is no need to give a separate call in the elevator car.
There are many types of call allocation methods and each elevator manufacturer has its own methods for implementing efficient call allocation that satisfies the elevator user. Each method, of course, includes numerous specific parameters that have the purpose of affecting the operation of the method. The control can be arranged such that e.g. the most suitable set of parameters for each situation are taken into use in different traffic situations. This is to give the elevator system the opportunity to adapt its operation to be the most suitable in respect of the prevailing traffic situation. A traffic situation can be e.g. a peak-hour situation, when the system registers a lot of simultaneous landing calls or destination calls.
One effective prior-art allocation method for elevators is the use of genetic algorithms especially in systems containing a number of elevators. Genetic algorithms are described in e.g. Finnish patent publication FI112856B. Genetic algorithms do not absolutely guarantee finding the most optimal value, but results achieved in practical applications are very close to it.
If an exceptional incident occurs or a threatening situation exists in a building, which can pose a danger to the users of the building, it is important to enable a safe exit of the users from the building. This kind of serious exceptional incident can be e.g. a fire, an earthquake, a bomb threat or similar type of event, which is of danger to the people in the building. An evacuation order can be given for the building after detecting an exceptional incident, either for certain floors of the building or for the entire building. The transport systems located in the building, such as elevators, are in this case placed in an important role.
Generally all use of an elevator in the event of fire is separately prohibited. This is because a fire can seriously damage an elevator system, in which case elevators are no longer safe to use for evacuating people to the exit floor of the building. It is possible that the elevator stops working during an elevator run, in which case the elevator car may stop between floors leaving the elevator passengers trapped. In addition, a fire or smoke may spread strongly, especially along the elevator shaft, in which case the elevator is no longer a safe place owing to the lack of oxygen or the heat. Also the extinguishing water used for extinguishing fires may damage the electrical parts of the system e.g. by causing short-circuits in the electronics parts of the system.
Additionally in the event of a fire it is not sensible to direct the elevator car to, and then open the doors to, a floor on which the fire has progressed to an advanced stage. In this case the safety of the people already traveling in the elevator is endangered and the time needed for evacuation becomes longer, if in addition it can be assumed that people have been evacuated from this kind of floor earlier.
On the other hand, if the elevator system or a part of it is constructed to be such that it withstands heat well by protecting the elevator shafts and elevator machines with suitable structures, the elevator system can very well be a feasible additional aid in the evacuation of the building. In high-rise buildings this is especially prominent, because the safe evacuation of a large number of people along the stairs and out of the building is extremely slow. If the elevators can be safely and reasonably controlled during an emergency, the evacuation time can be substantially shortened. It follows from the above that travel of the elevators in emergencies must be controlled in accordance with a special evacuation mode.
Additionally, when considering the energy requirement of an elevator system it is important to take into account a situation in which the electricity supply for some reason is unexpectedly disconnected. When the normal electricity supply disconnects, the emergency generator of the building should start, if this type of generator is available to the elevators. Emergency power is not normally sufficient for the needs of the whole elevator group (if it is a case of a large elevator group), but instead Emergency Power Drive (EPD) of the elevators is conventionally implemented such that an elevator or elevators is/are pre-selected, which serve passengers during emergency power use caused by an exceptional situation.
In the event of a power outage an elevator containing passengers can stop between floors. In this case in prior art when the emergency generator has started the elevator group control returns the elevators one at a time in a pre-defined sequence to the homing floor (generally the lobby), at which the passengers can exit the elevator. After this homing phase the aforementioned pre-defined elevators are placed into normal service (as “full service elevators”). The number of these type of elevators placed into service depends on the power and power requirement of the emergency generator, which the elevators in the worst case will require. The loading of the elevator car and the counterweight are almost always unbalanced and moving the elevator in the so-called light direction (empty car upwards, full car downwards) requires less power than in the so-called heavy direction (empty car downwards, full car upwards). Modern elevator drives can even return the latent potential energy of passengers back to the electricity network—i.e. function as a generator when driving in the light direction or when the elevators decelerate.
In modern skyscrapers, which are completed and which will be completed in the near future especially in South-East Asia, there may be up to 200 people on one floor if the building is in office use. Studies have shown that in buildings of about twelve stories and higher, elevators function more efficiently in emptying the building than stairs, if these two are alternatives to each other.
In the USA smoke detectors and heat detectors are used in elevator shafts, by means of which a fire that has ignited in the elevator shaft or its proximity can be detected. Use of the elevators is permitted in emergencies if the detectors have not triggered.
Publication U.S. Pat. No. 6,000,505 presents an appliance, with which a multiple level building can be evacuated during a fire incident using the elevator system. The appliance includes smoke detectors positioned on different floors. Elevator traffic is directed from the floors to be evacuated to the exit floor such that the doors of the elevator do not open on those floors on which a smoke detector detects smoke. The appliance also includes an emergency power source. One problem in the arrangement according to publication U.S. Pat. No. 6,000,505 is that the appliance is not able to forecast its own endurance and a consequence of this can be that the elevator could be performing an evacuation task at exactly the moment some critical component fails owing to e.g. strong heat in a fire incident.
A problem of prior art is that an effective evacuation method in a building in which both the stairways and the elevators can be used for evacuation has not previously been presented. Neither have all the parameters, with which the speed of evacuation can be influenced, been taken into account in prior art technology.